1. Field of the Invention
The present invention relates to a coupling arrangement including an optical photo-conductive (OPC) drum and a flange (e.g., a driving flange and/or a driven flange) in an electro-photographic (EP) machine, and more particularly to a coupling arrangement including a protrusion of the OPC drum disposed in a receiving portion of the flange.
2. Discussion of the Related Art
In a known electro-photographic (EP) machine, such as a photocopier, a laser printer, and a facsimile, a known process cartridge is removably mounted to a known main assembly.
The main assembly of the EP machine generally includes, among other components, a housing, a control panel disposed within the housing for controlling an image forming process, an electronic control system that is operated by the control panel, a motor that is controlled by the control system, a gear train that is driven by the motor, and electrical contacts for delivering power to the process cartridge that is inserted into and retained within grooves or channels formed in opposing side walls of the housing. The main assembly generally also includes an optical projection system and a central processor that controls a sequence and a timing of the optical projection system during a known image forming operation.
The process cartridge generally includes, among other components, an optical photo-conductive (OPC) drum, and a driving gear for driving one or more components of the process cartridge, such as a charging device, a developing device, and a cleaning device.
During the known image forming operation, the OPC drum undergoes a charging portion and a discharging portion of a charging/discharging cycle to ultimately create a developer image (e.g., a toner image) on a recording material (e.g., a sheet of paper, a transparent sheet, etc.). Briefly, during the charging portion of the charging/discharging cycle, the charging device uniformly charges an exterior surface of the OPC drum. The optical projection system projects image containing information in the form of a laser light to selectively discharge a portion of the exterior surface of the OPC drum, thereby forming a latent image on the OPC drum. The developing device applies a developer (e.g., a toner) to the partially charged exterior surface of the OPC drum. The developer is electro-statically attracted to the charged areas of the OPC drum, thereby forming the developer image. The developer image is then transferred from the exterior surface of the OPC drum to the recording material.
In the known process cartridge, the exterior surface of the OPC drum is coated with an electrically resistive coating to improve a quality of the image produced during the image forming process. Examples of known electrically resistive coatings include hard anodization with aluminum oxide (Al2O3) and oxidized surfaces. Generally, during a coating process, the OPC drum is submerged in the electrically resistive coating, such that an interior surface of the OPC drum, as well as the exterior surface, is coated with the electrically resistive coating.
It is known that the coated interior surface of the OPC drum must be sufficiently grounded for the OPC drum to undergo the required discharging portion of the charging/discharging cycle. In a known grounding or earthing arrangement, a grounding plate is disposed beneath the driving gear and within an interior portion of the OPC drum. The grounding plate includes a plurality of first radially extending projections that contact the interior surface of the OPC drum. To satisfactorily ground the OPC drum with the coated interior surface, the electrically resistive coating must be removed from a contact area of the interior surface through a separate and additional process (i.e., a process after the coating of the OPC drum), such that the first projections can achieve electrical connection with the interior surface of the OPC drum. An example of a known process for removing the electrically resistive coating includes a laser scribing operation. The grounding plate also includes a plurality of second radially extending projections that contact an electrically conductive shaft extending through the driving gear.
Thus, during assembly of the known process cartridge, the grounding plate is aligned with and inserted into the OPC drum, such that the first projections of the grounding plate achieve electrical connection with the contact areas of the OPC drum. The driving gear is then secured to the OPC drum by known securing means, thereby preventing relative movement and rotation, and preventing disassembly, among the OPC drum, the driving gear, and the grounding plate. Examples of securing means include an adhesive and a press fit arrangement. The electrically conductive shaft extends through the driving gear, and achieves electrical connection with the second projections of the grounding plate. By these arrangements, the OPC drum is sufficiently grounded through the grounding plate and the electrically conductive shaft.
However, the known OPC drum assembly suffers from a number of disadvantages. For example, during curing of the adhesive, care must be taken to maintain precise alignment and to prevent relative rotation and movement of the driving gear and the grounding plate relative to the OPC drum. Failure to maintain precise alignment may result in failure to achieve sufficient grounding of the OPC drum. The requirement to maintain precise alignment acts as an impediment to an automatic assembly of the OPC drum assembly. Further, the inadvertent use of an undesirably large volume of adhesive may result in adhesive flow into undesired portions of the known OPC drum assembly, and may degrade performance of the OPC drum assembly. The use of an undesirably small volume of adhesive may result in poor bond formation and inadequate bond strength between the OPC drum and the driving gear, and may reduce a useful life of the OPC drum assembly. Further, the press fit arrangement requires a relatively high degree of mechanical precision of each of the OPC drum and the driving gear (e.g., tolerances related to cylindricity of the driving gear and the OPC drum) to achieve satisfactory securing of the OPC drum and the driving gear. Such disadvantages increase a manufacturing time and/or a manufacturing cost of the known OPC drum assembly.